URL stands for Uniform Resource Locator. It's the posh technical term for a web address. Web addresses normally take the form http://www.somesite.com/somepage.html, which is not too much of a problem. But some site names can get very long, and so can page names. The increased use of database-driven sites mean that URLs can get very long indeed, and most of them is computer gobbledygook. They are impossible to type in, if you are reading them in a print article, and often get corrupted by word-wrapping when they appear in an email or blog posting.

An URL shortener is a web service that takes a long address that's hard to type, and turns it into a short one. You should use them in articles for print publication, classified ads, emails, blog and forum postings, anywhere there is a danger that the full address may be corrupted, or that someone may need to type the address into a browser manually.

But there is a danger in using short URLs that may make people afraid to use them. The short address disguises the real destination. This makes it easy for somebody to post an innocent looking message encouraging people to click on a link that takes them to a site which infects their computer with spyware, or something equally undesirable.

Some URL shortening services have tried to address this problem. The most well-known service, TinyURL.com, has an optional preview page that shows you the target address before you go there. But you have to know to type "preview" in front of the address, or visit the site and set it as a permanent option. Those who don't know about this are still vulnerable to deception.

A safe URL shortener would not allow the creation of links to undesirable sites. It would also always display a preview page, so the user always sees where the link is taking them before they go there. xaddr.com uses Internet blacklists to prevent its use to disguise sites that are advertised by spam. Its preview page offers a link to McAfee's Site Advisor, which can be used to check the safety of the destination.

Next time you need to write a long web address, use an URL shortener. But to encourage confidence that no harm will come from clicking the link, pick a safe one.